Conventionally, in order to record and analyze movements of workers in a factory and movements of shoppers in a store, traffic line creation devices that create a traffic line representing a motion trace of the tracking target have been used. For example, the traffic line creation device photographs a target space by a camera installed in a relatively higher place, recognizes a tracking target (for example, a person) from a photographed image, tracks it, and creates a traffic line.
As mentioned above, the traffic line is to track the position of the tracking target projected in the image in the target space. Therefore, a movement in a vertical direction (the y direction) of the tracking target within the image space represents a movement of the tracking target in a front direction or a depth direction viewed from the camera in the target space. Also, a movement in a lateral direction (the x direction) of the tracking target within the image space represents a movement of the tracking target in a left or right direction viewed from the camera in the target space.
For example, in the conventional traffic line creation device, in order to create a traffic line, the traffic line is created by recognizing a tracking target in the image, creating rectangular frames including the tracking target, and connecting the center points of the frames in a constant time interval (for example, see Patent Literature 1).